JAX-RS/Rest: Set a parameter multiple times, or use a single comma-delimited parameter?

Question

I read that the HTTP way to pass an array in a request is to set a parameter multiple times:

1) GET /users?orderBy=last_name&orderBy=first_name

However, I've also seen the comma-delimited parameter (and I feel this is "cleaner"):

2) GET /users?orderBy=last_name,first_name

I want to implement multi-sorting (ordering users by last_name, then duplicate last_names are ordered by first_name). Code-wise, this is easy (Google's Guava libraries to the rescue), but how should I expose this? Does the first way even preserve the order of the fields (sort by last_name, then by first_name)?

Spring will magically convert a parameter into a String[] array, if it is set multiple times in the request:

... @RequestParam("orderBy") String[] orderBy ... becomes ["last_name","first_name"]

This leads me to believe the first way is considered best-practice, although I like the second way...

Answer 1

The first method is the preferred, standard way.

You can certainly use the second way, but you will have to implement your own way of tokenizing the request parameter value, with all the issues that involves. For example, consider what happens if one of your values contains a ',' character.

Because the first is quite standard, it has the benefit of fitting in nicely with jax-rs, and validation frameworks; because we always validate our inputs, right? ;)